1. Field of the Invention
This invention relates to digital cameras and, more particularly, to a digital camera adapted for taking pictures of a subject in a continuous manner while varying exposure therefor.
2. Description of the Prior Art
The function possessed by the silver-halide photographic cameras includes a continuous shot function to take pictures of a subject in a continuous fashion while varying exposure. Using this function, it is possible to take at least one picture of a subject with a best suited exposure. In the silver-halide photographic camera, image recording completes simultaneous with image exposure, making it possible to advance the timing of picture taking during continuous shot operation in proportion to increase in film feed rate.
In the digital camera, however, the processes of exposure by a CCD imager and transfer of pixel signals from the CCD imager each require a 1-frame period. Only these two processes needs a time of as long as a 2-frame period. Considering further an image recording time, signal processing for one shot would require a 2-frame period or longer. Thus, the digital camera has had a problem of delay in picture taking timing, as compared to the silver-halide photographic camera.
Meanwhile, the processes of exposure, data transfer and recording are dependent from one another. It can be considered that the picture taking timing is to be advanced if the signal processing of a preceding shot and that of a current shot be made in a time-overlap manner. In the continuous shot function, however, exposure must be changed for each shot. To achieve this, if the signal processes be overlapped in time one another, there is a fear that proper update of exposure is difficult resulting in poor operation in a continuous shot function.